One Editor To Rule Them All Dan Berger Titus Winters

Introduction  The hacker community has a tradition of treating their favorite text editor with a reverence bordering on religious fanaticism… Editor wars are usually fought between the devottees of Emacs and vi, the most popular editors on Unix. -

Outline  A Brief Emacs history  Fundamental Emacs Concepts  Basic Commands/Key Chords  Using Emacs as an IDE  “Nifty” Features  Customizing Emacs

Emacs: A Brief History  Originally written in 1976 by Richard Stallman (scary dude) as a set of Editor MACroS for the TECO editor.  Two common strains in the wild: Emacs (the one we’re talking about here) and XEmacs (the one we’re not).  If you want to know more: try WikiPedia/wiki/Emacs

Fundamental Emacs Ideas  Emacs is essentially a lisp interpreter.  No – this isn’t an elisp hacking seminar.  What’s important is that elisp is Turing complete;  That means Emacs is horribly extensible – and can do anything you can express in elisp (see Turing Complete)

Terminology  A “key chord” is a set of keys pressed together.  Text is stored in “buffers” – often, but not always, buffers hold the contents of files.  Reading a file into a buffer is called “visiting” the file.  Portions of the emacs display are called “windows”  Multiple emacs displays are each called a “frame”

More Emacs Ideas  Emacs does its work by calling elisp functions – which are often bound to key chords.  Buffers have associated major and minor editing modes – so the editor can behave differently when you’re editing C/C++ code vs. Python code.

Basic Commands (I)  Starting emacs:  emacs [-nw] [file1 file2 … fileN]  emacs will run either in GUI mode (under X) or tty mode (in a terminal, or with the –nw flag)  Exiting emacs:  C-x C-c  Control-”x” Control-”c”  M-x save-buffers-kill-emacs  Meta (Alt or Esc)-”x” “save-buffers-kill-emacs”

Basic Commands (II)  Get help: C-h  Run a tutorial: C-h t  Open (visit) a file: C-x C-f  Save a buffer to a file: C-x C-s

Mark and Selection  Manipulating regions of text is easy – once you understand “the mark”  The mark is one end of the region you want to work on – the other end is determined by “the point” – which is the current cursor position.  Set the mark: C-spc

Manipulating Regions  Many emacs commands (can) work on a region of text. Remember – a region is between the mark and the cursor (point).  Examples:  C-w will “kill” (cut) the selected region  Esc-w will copy the selected region  C-y “yanks” (pastes) it back  M-x ispell-region will spell check the selected region of text.

Emacs as an IDE  Emacs was written by developers for developers – so it’s not surprising that it makes a pretty good IDE. You can:  Write code  Navigate code  Compile code  Debug Code  Interface with revision control (CVS)

Writing Code  Emacs has major modes for just about every language you can imagine.  It will perform syntax-aware indentation, can colorize the code, and is generally “aware” of the structure of the code. So you can jump around basic blocks, functions, etc.  Each major mode is different – C-h m will describe the current modes.

Navigating Code  Emacs includes a support program called etags – it builds a cross reference (index) of a set of files, and helps emacs find symbols.  Complete use is outside the scope of this talk, but Google can help.

Compiling  Simple: M-x compile  By default emacs will run Make – but you can run any command you want.  It will cd into the directory containing the file you were visiting when you invoked the compile.  This means that you may have to tell make which Makefile to use, if it’s not in that directory.

Debugging  GUD – Grand Unified Debugger mode – knows how to interface with many “standard” unix debuggers, including gdb (and dbx)  M-x gdb  M-x pdb  M-x jdb  An example is worth a thousand words…

CVS Integration  Emacs will recognize if a file (directory) is managed by CVS – and give you a set of CVS commands you can perform without leaving the editor including;  Checkout a file  Commit changes to a file  Diff a file against the repository  Register a new file with revision control

Nifty Features  font-lock-mode  flyspell-mode  M-x ispell-comments-and-strings  ediff mode  tramp

Font-Lock-Mode  Provides syntax hi-lighting for languages emacs understands (many).  You can customize the colors it uses – and the face (font).  Turn it on with:  M-x font-lock-mode  Colorize your world with:  M-x font-lock-fontify-buffer

Flyspell-Mode  On-the-FLY spell checking.  Turn it on with M-x flyspell-mode  As you move across text, it get’s spell checked. Errors are marked.  If you want to spell check the entire buffer,  M-x flyspell-buffer  To see suggested spellings, place the point (cursor) on the misspelled word and middle- click (or press Esc-$)

M-x ispell-comments  Just what it sounds like – it will spell-check your code – paying attention to comments and strings (between quotes).

ediff mode  diff (the file comparison tool) on steriods.  Give emacs two (or three!) files to compare – and it will help you navigate the differences – making it easy to update one file with the changes in another.  M-x ediff-files  M-x ediff-buffers

tramp  A tool for opening files that are not local over SSH  Any file (anywhere) can be represented as  i.e.:  Very low bandwidth – so it’s usable over slow/unreliable links.  Not in the standard Emacs package, but should be installed on CS machines “soon.”

Tramp (cont.)  If you want to install it on a personal machine (Linux or Windows), you can fetch it from: 

Customizing Emacs  On startup, emacs reads and evaluates ~/.emacs – which can contain arbitrary elisp code you want executed on startup.  My.emacs file (~dberger/.emacs) is world readable – let’s take a quick look at it now…  Recent versions of emacs also include a package to help you customize emacs – M-x customize will get you started.

Emacs on MS Windows   The windows portions of Dan’s.emacs file are old – and not “supported.”  I haven’t used Windows in years – so I’ve no idea if that config is still needed or functional.

Stuff We Didn’t Cover  Emacs can be a mail reader, web browser, psychologist, and much, much more.  We didn’t cover elisp – the lisp dialect that emacs uses – there’s a good tutorial on-line:  intro/